Atherosclerosis is a disease which affects the blood vessels in a cardiovascular system. This disease involves thickening of the vessel walls caused by the accumulation of fat, fibrin, cellular debris and/or calcium. As the vessel wall thickens, the internal lumen of the vessel narrows. This is commonly referred to as stenosis. Vessel stenosis impedes and reduces blood flow through the vessel. Hypertension and disfunction can result in organs which are downstream from the vessel stenosis due to the reduced blood flow.
One complication associated with the thickening of the vessel is the loss of its ability to expand and contract. Additionally, the thickening of the vessel wall reduces the vessels viability. This results in increased likelihood that an aneurysm will develop. If the patient suffers from hypertension or elevated blood pressure, ann developing aneurysm will frequently dissect and ultimately rupture.
Small vessels, such as the arteries that supply blood to the heart, legs and intestines are particularly susceptible to atherosclerotic narrowing. The loss of blood supply to the leg or segment of the intestine may result in the development of gangrene. Atherosclerotic narrowing of the coronary arteries impedes, limits and, in some instances, prevents blood flow to regional areas of the heart. Depending upon the severity of the narrowing and its location within the coronary circulation, pain, cardiac dysfunction or death may result. Larger vessels can also develop atherosclerosis.
In cases where atherosclerotic disease is advanced and the attendant complications jeopardize the health of the patient, surgical intervention is usually instituted. If the disease is extensive and the vessel is no longer reliable, it is usually replaced or bypassed by a graft. Conventionally this procedure involves placing the patient on a heart bypass machine while the diseased portion of the vessel is transected and removed. A graft, either synthetic or biologic, is attached between the transected sections of the vessel. This grafting procedure is called anastomosis.
A biologic graft is usually a non-critical artery or vein of small diameter which is harvested from elsewhere in the body, such as the internal mammary artery. When no suitable artery or vein can be harvested, or where time prevents harvesting of a suitable biological vessel, a synthetic vessel can be used. Synthetic vessel are conduits made from biocompatible material, such as DACRON.RTM. polyester fiber (DACRON is a registered trademark of E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.), or polytetrafluoride (PTFE).
As described above, conventional heart bypass surgery requires that the patient be placed on a heart-lung machine and stoppage of the blood flow along the diseased vessel. This is a very time consuming procedure. Moreover, placing a patient on an extracorporeal circuit may result in complications, such as a stroke, myocardial infarction, infection, or hemorrhage.
A need, therefore, exists for a bypass procedure which eliminates the need for placing the patient on an extracorporeal circuit. A need also exists for a bypass procedure which minimizes the likelihood of damage to the host vessel.